Freeze injury ranges from worse than to not as bad as expected

Southwest wheat farmers either dodged a bullet or took one in the head, depending on where they were located, what stage of growth the wheat had reached and how cold it got and how long temperatures remained at damaging levels.

Wheat that had shown the highest yield potential appears to have been hardest hit. Later-emerging wheat may not have been mature enough to suffer as much damage. But drought that delayed emergence and early growth had already limited yield potential of some of that less mature wheat crop.

“On April 4th, I toured southwest Oklahoma. In my experience, most freeze events are overhyped; however, this one was the real deal. I traveled from Faxon to Chattanooga to Altus to Blair and ended up at Apache. Damage was similar at all sites, with injury ranging from 50 percent to 80 percent.”

He says the best wheat was damaged most. “The best looking wheat was the hardest hit,” he said. “Particularly troubling are some fields in the Altus area that easily had 80-bushel potential prior to the freeze. In most of these fields, we are too far past the tillering stage to have yield compensation from secondary tillers. Late-emerging fields that were jointing or smaller escaped the freeze with little injury.

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“Fields that had been heavily grazed and/or under-fertilized also escaped with relatively minor injury. Conditions improved slightly on wheat in the Chickasha area with injury more in the 10 percent to 30 percent range.”

He’s not optimistic about recovery for badly damaged wheat. “I’m frequently asked if the injured wheat head will go ahead and ‘push through’ as the season progresses, and the answer is no. If you see heads emerging out of the boot in a few weeks, they are likely not damaged and a head count at this stage will be a reasonable estimate of fertile heads. Since there will not be additional stem elongation in freeze-injured wheat, it will not accumulate as much tonnage as in a ‘normal’ year.”

Field conditions are variable. “Freeze injury can vary greatly among fields and even within a field. So, it is important to check several sites within a field and split several stems when determining the percent injury,” he said. “Check early-maturing varieties such as Jackpot, Billings, and Everest first, as they are most likely to have injury.”

Texas update

Central Texas wheat suffered considerable damage from the late-March freeze, but it could have been a lot worse, according to a Texas A&M AgriLife Extension Service crops expert.

“We still don’t know the full extent of the damage,” said Dr. Travis Miller, AgriLife Extension agronomist and Texas A&M University soil and crop sciences associate department head. “Some areas were pretty severely hit and some less so.”

During early April, Miller, Dr. Gaylon Morgan and Dr. Clark Neely, also AgriLife Extension agronomists, along with county agents, toured various sites and conducted wheat-freeze clinics in the Blacklands, where wheat was more mature and more likely to suffer damage from temperatures that in some cases dropped into the mid-20s.

“The good news appears to come from the High Plains. Although there were some reports of injury, it was not extensive – just a little here and there,” Miller said.

In Central Texas, where there was more damage from the March freeze, it’s still hard to estimate how many acres of wheat were damaged.

“It’s a situation where the upper part of your field may be okay, and the lower third of it may have 20 percent or 25 percent damage. You just struggle to get a number on something like that.”

Miller and his colleagues saw two types of injury during their wheat-freeze clinics.

“We saw lot of sterilization of heads,” he said. “And we had stem injury where it ruptured the water- and nutrient-carrying vessels in the stem, and the plant just quit carrying water and the leaves were drying up. (We saw) some of both kinds of damage, but obviously the plant can’t recover if the growing point or the head freezes. It just dies.”

Miller and his colleagues reported quite a bit of freeze injury to corn, but say the crop will generally recover.

“Overall, the damage was not nearly as extensive as I’ve seen from some freezes in the past,” Miller said. “Certainly, if you’re one of those farmers who had more advanced wheat, it looks pretty severe to you.”

Less damage in the Plains

Further north, damage seems less severe. Dr. Jackie Rudd, AgriLife Research wheat breeder in Amarillo, scouted fields in both the Deaf Smith County area and in the Rolling Plains. He said leaf burn is showing on the wheat plants, but most of the wheat hit by freezing temperatures was not advanced enough to get major damage.

“There will be some leaf burn and upper canopy damage, but the young immature heads did not appear to be damaged,” Rudd said. “The canopy will grow out of the damage,and yields will not be hurt by this single stressor.”

If the wheat was already under stress or is stressed further due to insects or drought, the damage could increase.

Rudd explained that wheat in the vegetative state is not susceptible to freeze, but once the head of the plant emerges above ground, it can be damaged and suffer yield loss. The higher the head is above the ground, the more exposed it becomes.

Research plots at Chillicothe had heads 2 inches to 3 inches above ground where temperatures reached 25 degrees, but the canopy and ground temperature appeared to provide some protection.

“It will vary field by field where there might have been pockets of colder temperatures,” Rudd said. “In 2009, the Rolling Plains lost a significant amount of wheat to an April 5 freeze when the crop was further along. But I think we might be okay in most of that area this time because we were not as far along.

“The foliage here will recover if it already had good moisture or receives good rain,” he said. “But it does need rain.”

Rick Minzenmayer, Texas AgriLife Extension specialist for Green and Runnels Counties, in the Southern Rolling Plains, says freeze injury was not as damaging to wheat as the prolonged drought.

“Wheat looked pretty good in December and early January,” Minzenmayer said during the recent Concho Valley Cotton Conference, held every two years in San Angelo. “Typically, we get rainfall in February but we didn’t get it this year and wheat has gone back rapidly. It is extremely dry. I expect much of the wheat acreage to be zeroed out.”

Minzenmayer says much of that acreage could go back to cotton, which has a better option for insurance coverage than other crops.

Jim Swart, Texas AgriLife Extension IPM specialist in Commerce, says he’s not as pessimistic about the wheat outlook as he was shortly after the freeze.

“I am more encouraged by what I recently found in the wheat,” he said.

As is the case across the region, the more mature, early-emerged wheat was more vulnerable.

“The older wheat has sustained significant damage from the freeze that occurred two weeks ago,” Swart said. “Many of the plants I saw headed appear to be sterile, which means the anthers have been damaged by the cold. The heads look normal but the anthers are green and will not produce viable pollen.”

Younger wheat may be less damaged. “Plants that were jointed but less developed at the time of the freeze have developing heads that appear to be normal. We will know for sure when heading, and hopefully, pollination occurs.”

In most years, wheat planted in late October or early November in the Northeast corner of Texas, offers the best opportunity for profitable yields. That may not be the case this year.

“The wheat that sprouted following the Christmas rain and snow event appears to be unaffected by the freeze,” Swart said. “The heads look normal and healthy, and will likely pollinate when they emerge from the boot. We will continue to monitor the situation and provide weekly updates.”

Almost 80 percent of the wheat in Texas is grown in the High Plains and Rolling Plains region. The remaining crop is grown in the Central and North Central regions.

Thanks to Robert Burns and Kay Ledbetter, AgriLife Extension for Texas crop updates.